Auto merge of #42481 - brson:wingnu, r=alexcrichton

Fix setting PATH during linkage on windows-gnu

This makes the behavior almost exactly the same as before the VS2017 patch, except that on MSVC builds the host bin path is no longer added to PATH. I am not sure that's actually necessary on any platform.

r? @alexcrichton

Fixes https://github.com/rust-lang/rust/issues/42422